Sleep and brain health

Abstract

Stroke is the second cause of death and one of the leading causes of disability. 1 Worldwide, fifteen million people suffer a stroke every year, nearly six million die, and around five million are left permanently disabled. 2,3 The identification of the risk factors of stroke, especially those that can be modified, is of paramount relevance to control the burden of cerebrovascular diseases. 4,5 In the current issue of The Journal of Clinical Hypertension, the study by Dr Hua and colleagues aimed to examine the association between sleep duration and stroke risk in middle-aged and elderly population. 6 The cross-sectional study included 10 516 participants aged ≥45 years from the China Hypertension Survey study, a nationally representative cross-sectional survey designed to provide reliable and evidence-based data on the current status of hypertension and associated factors in Chinese adults. Longer sleep duration was associated with higher prevalence of stroke: the relationship resulted linear in non-hypertensive patients with a turning point of the smooth curve at 8 hours, whereas a threshold effect was found in hypertensive individuals. 6 Despite methodological issues inherent to the cross-sectional and self-reported nature of data, which may be subjected to recall biases and possible residual or unmeasured confounders, the study can offer intriguing insights for the understanding of behavioral contributors to stroke. | S LEEP DUR ATI ON AND S TROK E RIS KSleep is a tightly regulated phenomenon that takes up approximately to one-third of our lifetime. Although the actual purposes of sleep are still to be fully elucidated, there is indisputable evidence that it serves essential functions and affects many physiological processes.The average need for adults is between 7 and 9 hours of sound sleep per day on a regular basis, and deviations from such rhythm can have negative consequences for health. Epidemiological studies investigating the putative effect of habitual sleep on cerebrovascular risk demonstrated a J-shaped association between sleep duration and stroke incidence. Both insufficient and excessive sleep are predictors for future stroke, and the association is stronger for long than short sleep. 7 It has been estimated that every 1-hour increase in sleep duration can increase the risk of stroke by 10%-15% and individuals sleeping more than 8 hours can be approximately 50% more susceptible to stroke than those with normal sleep duration through 10 years of observation. 8Notably, this trend has been consistently identified across studies irrespective of nationality or ethnicity and after the adjustment for potential confounders like education, employment status, family income, depression, physical activities, and sleep-disordered breathing-related symptoms.Interestingly, sleep duration can significantly affect the traditional risk factors for stroke. The Sleep Hearth Health Study was the first one to suggest that the relationship between sleep duration and hypertension follows a U-shaped curve, being both sho...